Generally there are two principal ways in which starch can be processed. First, starch can be chemically modified in water or solvents and dried, resulting in whole, individual starch granules. This is the type of starch used in puddings which require cooking. Secondly, if an instant water soluble starch is needed, the starch is pregelatinized by, for example, passing a starch slurry over a drum dryer. The drum dryer simultaneously cooks and dries the starch in cold water swellable sheets. This type of starch is used in instant puddings.
A starch which is modified is one in which physical properties such as viscosity, texture, dispersibility, stability and syneresis are altered. The important chemical means of making these kinds of changes are acid hydrolysis, oxidation, crosslinking esterification and etherification. However, associated with some chemical modifications are undesirable by-products or residues (e.g., clorohydrin residues, etc.). Another suggested means is the creation of an osmotic condition by the addition of various salts to a starch slurry prior to gelatinization in order to inhibit bursting of starch granules by controlling swelling of the granules. However, the resultant starch granules generally do not fully swell and lack uniformity in the degree of gelatinization thus producing a starch which is substantially inferior to the chemically modified starches.
It thus becomes a feature of this invention to provide a process for the modification of starch but without undesirable by-products or residues.
It is a further feature of this invention to produce a physically modified pregelatinized starch having properties of a chemically modified pregelatinized starch.